In order to control the flow of fluid, there is employed a control valve for driving a valve element to move in the axial direction with respect to a casing and varying a clearance between the outlet of the casing and the tip of the valve element to thereby control the output flow rate or the output pressure of the fluid. For example, the flow of the fluid is blocked by bringing the outlet of the casing into contact with the tip of the valve element, and the fluid is allowed to flow by separating the outlet of the casing and the tip of the valve element. By repeating the contact and separation, precise adjustment of the flow rate or the pressure of the fluid is achieved.
For example, in JP-A-2005-273704, as regards a valve mechanism used for purging (exhausting) exhaust gas including water from a fuel cell to the outside, there is described a valve device including a valve element which is provided at the tip of a shaft inserted into a core member and hence supported thereby and driven by a solenoid so as to be capable of advancing and retracting in the axial direction, the valve device blocking a flow passage by the valve element being seated on a valve seat, and allowing fluid to flow into the flow passage by the valve element being separated from the valve seat.
In the fluid control valve which blocks the flow passage or allows the fluid to flow into the flow passage by bringing the tip of the valve element into contact with or separated from the fluid outlet of the casing, a shaft portion of the valve element is supported by the casing so as to be capable of advancing and retracting as described in JP-A-2005-273704. Therefore, a supporting portion is worn by the sliding movement as the movement of advancing and retracting is repeated. When the abrasion progresses, the advancing and retracting movement of the valve element in the axial direction might be deviated, which may result in incomplete blockage of the flow passage. Also, abrasion powder which is generated by abrasion might flow with the fluid, and contaminate the downstream side.
An object of the present invention is to provide a fluid control valve which is able to restrain abrasion of a part between a valve element and a casing when the tip of the valve element is moved with respect to a fluid outlet of the casing.